In the art a number of no-dig methods for repairing underground pipes are used. Common for most of these methods and devices used in the methods is the fact that they seek out the point of the pipe where breakage or damage has occurred and with various means removes any debris resulting from the damage. At this point a number of different methods find use, for example in one method a very long and thin “stocking” is introduced into the pipe section which stocking afterwards is inflated and a hardenable mass, for example an epoxy is applied to the inside of the stocking thereby creating a new interior pipe inside the existing pipe in a relining process.
Other systems include the use of a packer where a suitable packer is selected depending on the size of the pipe, the distance to the damage, the extent of the damage etc. Before the packer is positioned in the damaged area, repair materials, typically in the shape of a reinforcement mat, for example a glass or carbon fibre mat impregnated with a hardenable mass, for example cement-based or epoxy-based, is arranged on the outside of the packer. These preparations (repair materials etc) are carried out outside the pipe in order for personnel to be able to carry out the process. Typically the works will be handled in a manhole or above ground. After having mixed the hardenable mass and positioned the mat correctly on the packer the packer is transported, i.e. pulled, pushed or otherwise moved along inside the pipe until it reaches the position where the repair patch/repair materials are to be applied to the damage in the underground pipe.
Once the packer reaches its desired position the packer is inflated whereby the repair materials are urged against the sidewall of the pipe. At this time the packer is left in place in order to allow the hardenable cement-based or epoxy-based mass to harden and adhere to the inside of the pipe. This process typically takes a few hours after which the packer is deflated and removed again leaving the repair patch/repair material in place, hopefully having repaired the damage to the pipe system.
These methods are all well-known in the art, but do have substantial disadvantages and drawbacks which the present invention addresses, particularly relating to the method implementing a packer.
The repair materials typically comprise some type of flexible mat, for example made from glass fibres or carbon fibres, which mat is suitable to be embedded in or impregnated with a hardenable mass, typically cement-based or epoxy-based. When working with hardenable masses there is typically a set period of time available (opening time) in order to mix and apply the material after which a certain period (setting time) is required before the material has reached its desired strength or the necessary strength in order to remove the scaffolding, in this case the packer. Normally, the fast reaction time (setting time) and thereby the less time consuming process also only leaves the minimum time available for applying the material to the packer (opening time), position the packer in the correct position relative to the damage to the pipe and inflating the packer in the desired position for the required setting time. It would be desirable to have a longer working time, i.e. more time to prepare the mixture and the repair patch on the packer and more time to guide and introduce the packer into the correct position in the damaged pipe system and time to inflate and ensure that the packer is in the correct position before the open time of the material has run out, i.e. before it sets such that it becomes impossible to work. Therefore a longer opening time is desirable and at the same time a shorter setting time is desirable, in that once the packer is inflated and urging the repair materials into the damaged part of the pipe, this time can only be used for putting things away, cleaning and waiting.
For typical products used for these processes the opening time can be selected for example as material having an opening time of 50 minutes which in turn requires four hours curing time or half an hour opening time requiring three hours hardening time, 15 minutes opening time requiring one and a half hour curing time and finally a very fast material only having an opening time of 8 minutes and requiring only half an hour curing time.
The opening time is used for mixing the materials which are typically two-component materials, i.e. a base material and a hardener, which needs to be mixed thoroughly in order to ensure a satisfying result, placing the repair materials on the flexible packer, introducing the packer into the correct position inside the pipe system and inflating the packer to a desired pressure in order to apply the repair materials in the correct position. Depending on how far the damaged area is from the nearest manhole, it is very often very difficult to use materials having a very fast reaction or short opening time. One factor which is advantageous to this part of the job is the fact that typically in a sewer the temperature will be 6-8° C. relatively constant around the year whereas the reaction times/opening times mentioned above are calculated at 20° C. The lower temperature will naturally slow down the chemical reactions and thereby increase the opening times allowing the workers more time to mix, place and position the repair materials in the correct position. It is, however, not significantly more time that may be obtained in this manner. On the other hand, the low temperature also provides a serious set-back for the process in that the setting time/curing time of the materials will also be substantially longer. The curing time is for personnel reasons to be considered mainly as wasted time, both with respect to the personnel waiting around for the patch to cure, but also for the investment in machinery and equipment which is used during the process. These factors naturally make the entire process overly costly in comparison with the work which is in fact achieved.